Nicolaus Copernicus

Nicolaus Copernicus (1473–1543) was a mathematician and astronomer
who proposed that the sun was stationary in the center of the universe
and the earth revolved around it. Disturbed by the failure of
Ptolemy's geocentric model of the universe to follow Aristotle's
requirement for the uniform circular motion of all celestial bodies
and determined to eliminate Ptolemy's equant, an imaginary point
around which the bodies seemed to follow that requirement, Copernicus
decided that he could achieve his goal only through a heliocentric
model. He thereby created a concept of a universe in which the
distances of the planets from the sun bore a direct relationship to
the size of their orbits. At the time Copernicus's heliocentric idea
was very controversial; nevertheless, it was the start of a change in
the way the world was viewed, and Copernicus came to be seen as the
initiator of the Scientific Revolution.

Nicolaus Copernicus was born on 19 February 1473, the youngest of
four children of Nicolaus Copernicus, Sr., a well-to-do merchant who
had moved to Torun from Cracow, and Barbara Watzenrode, the daughter
of a leading merchant family in Torun. The city, on the Vistula River,
had been an important inland port in the Hanseatic League. However,
fighting between the Order of the Teutonic Knights and the Prussian
Union in alliance with the Kingdom of Poland ended in 1466, and West
Prussia, which included Torun, was ceded to Poland, and Torun was
declared a free city of the Polish kingdom. Thus the child of a German
family was a subject of the Polish crown.

The father died in 1483, and the children's maternal uncle, Lucas
Watzenrode (1447–1512), took them under his protection. Watzenrode was
a very successful cleric — he was to become bishop of Warmia
(Ermland in German) in 1489 — and he both facilitated his
nephew's advancement in the church and directed his education. In 1491
Copernicus enrolled in the University of Cracow. There is no record of
his having obtained a degree, which was not unusual at the time as he
did not need a bachelor's degree for his ecclesiastical career or even
to study for a higher degree. But the University of Cracow offered
courses in mathematics, astronomy, and astrology (see Goddu 25–33 on
all the university offerings), and Copernicus's interest was sparked,
which is attested to by his acquisition of books in these subjects
while at Cracow.[1]

In 1495 Watzenrode arranged Copernicus's election as canon of the
chapter of Frombork (Frauenberg in German) of the Cathedral Chapter of
Warmia, an administrative position just below that of bishop. He
assumed the post two years later, and his financial situation was
secure for life. In the meantime, following in his uncle's footsteps,
Copernicus went to the University of Bologna in 1496 to study canon
law (see Goddu part 2 on what Copernicus may have encountered in
Italy). While at Bologna he lived with the astronomy professor
Domenico Maria Novara and made his first astronomical observations. In
addition, as Rosen (1971, 323) noted, “In establishing close
contact with Novara, Copernicus met, perhaps for the first time in his
life, a mind that dared to challenge the authority of [Ptolemy] the
most eminent ancient writer in his chosen fields of study.”
Copernicus also gave a lecture on mathematics in Rome, which may have
focused on astronomy.

Copernicus's studies at Bologna provided an advantage he did not
have at Cracow — a teacher of Greek. Humanism began to
infiltrate the Italian universities in the fifteenth century. As
Grendler (510) remarked, “By the last quarter of the century,
practically all universities had one or several humanists, many of
them major scholars.” Antonio Cortesi Urceo, called Codro,
became professor at Bologna in 1482 and added Greek several years
later. Copernicus may have studied with him, for Copernicus translated
into Latin the letters of the seventh-century Byzantine author
Theophylactus Simocatta (MW 27–71) from the 1499 edition of a
collection of Greek letters produced by the Venetian humanist printer
Aldus Manutius. Aldus had dedicated his edition to Urceo. Copernicus
had his translation printed in 1509, his only publication prior to
the On the Revolutions (De revolutionibus). It is
important to note that Copernicus's acquisition of a good reading
knowledge of Greek was critical for his studies in astronomy because
major works by Greek astronomers, including Ptolemy, had not yet been
translated into Latin, the language of the universities at the
time.

Copernicus left Bologna for Frombork in 1501 without having
obtained his degree. The chapter then approved another leave of
absence for Copernicus to study medicine at the University of
Padua. The medical curriculum did not just include medicine, anatomy,
and the like when Copernicus studied it. Siraisi (1990, 16) noted that
“the reception in twefth-century western Europe of Greek and
Islamic technical astronomy and astrology fostered the development of
medical astrology…the actual practice of medical astrology was
greatest in the West between the fourteenth and the sixteenth
centuries.” Astrology was taught in the medical schools of
Italy. “The importance attached to the study of the stars in
medieval medical education derived from a general and widely held
belief that the heavenly bodies play an intermediary role in the
creation of things here below and continue to influence them
throughout their existence. The actual uses of astrology in medical
diagnosis and treatment by learned physicians were many and various.
‘Astrological medicine’ is a vague and unsatisfactory term
that can embrace any or all of the following: first, to pay attention
to the supposed effect of astrological birth signs or signs at
conception on the constitution and character of one's patients;
second, to vary treatment according to various celestial
conditions…third, to connect the doctrine of critical days in
illness with astrological features, usually phases of the moon; and
fourth, to predict or explain epidemics with reference to planetary
conjunctions, the appearance of comets, or weather conditions”
(Siraisi, 1981, 141–42). It is true that astrology required that
medical students acquire some grounding in astronomy; nevertheless,
it is likely that Copernicus studied astrology while at the
University of
Padua.[2]

Copernicus did not receive his medical degree from Padua; the
degree would have taken three years, and Copernicus had only been
granted a two-year leave of absence by his chapter. Instead he
matriculated in the University of Ferrara, from which he obtained a
doctorate in canon law. But he did not return to his chapter in
Frombork; rather he went to live with his uncle in the episcopal
palace in Lidzbark-Warminski (Heilsberg in German). Although he made some
astronomical observations, he was immersed in church politics, and
after his elderly uncle became ill in 1507, Copernicus was his
attending physician. Rosen (1971, 334–35) reasonably conjectured that
the bishop may have hoped that his nephew would be his successor, but
Copernicus left his uncle because his duties in Lidzbark-Warminski interfered
with his continuing pursuit of his studies in astronomy. He took up
residence in his chapter of Frombork in 1510 and stayed there the rest
of his life.

Not that leaving his uncle and moving to Frombork exempted
Copernicus from continued involvement in administrative and political
duties. He was responsible for the administration of various holdings,
which involved heading the provisioning fund, adjudicating disputes,
attending meetings, and keeping accounts and records. In response to
the problem he found with the local currency, he drafted an essay on
coinage (MW 176–215) in which he deplored the debasement of
the currency and made recommendations for reform. His manuscripts
were consulted by the leaders of both Prussia and Poland in their
attempts to stabilize the currency. He was a leader for West Prussia
in the war against the Teutonic Knights, which lasted from
1520–1525. He was physician for the bishop (his uncle had died in
1512) and members of the chapter, and he was consulting physician for
notables in East and West Prussia.

Nevertheless, Copernicus began to work on astronomy on his
own. Sometime between 1510 and 1514 he wrote an essay that has come to
be known as the Commentariolus (MW 75–126) that
introduced his new cosmological idea, the heliocentric universe, and
he sent copies to various astronomers. He continued making
astronomical observations whenever he could, hampered by the poor
position for observations in Frombork and his many pressing
responsibilities as canon. Nevertheless, he kept working on his
manuscript of On the Revolutions. He also wrote what is known as
Letter against Werner (MW 145–65) in 1524, a
critique of Johann Werner's “Letter concerning the Motion of the
Eighth Sphere” (De motu octavae sphaerae tractatus
primus). Copernicus claimed that Werner erred in his calculation
of time and his belief that before Ptolemy the movement of the fixed
stars was uniform, but Copernicus's letter did not refer to his
cosmological ideas.

In 1539 a young mathematician named Georg Joachim Rheticus
(1514–1574) from the University of Wittenberg came to study with
Copernicus. Rheticus brought Copernicus books in mathematics, in part
to show Copernicus the quality of printing that was available in the
German-speaking cities. He published an introduction to Copernicus's
ideas, the Narratio prima (First Report). Most importantly,
he convinced Copernicus to publish On the Revolutions.
Rheticus oversaw most of the printing of the book, and on 24 May 1543
Copernicus held a copy of the finished work on his deathbed.

Classical astronomy followed principles established by
Aristotle. Aristotle accepted the idea that there were four physical
elements — earth, water, air, and fire. He put the earth in the
center of the universe and contended that these elements were below
the moon, which was the closest celestial body. There were seven
planets, or wandering stars, because they had a course through the
zodiac in addition to traveling around the earth: the moon, Mercury,
Venus, the sun, Mars, Jupiter. Beyond that were the fixed stars. The
physical elements, according to Aristotle moved vertically, depending
on their ‘heaviness’ or ‘gravity’; the
celestial bodies were not physical but a ‘fifth element’
or ‘quintessence’ whose nature was to move in perfect
circles around the earth, making a daily rotation. Aristotle
envisioned the earth as the true center of all the circles or
‘orbs’ carrying the heavenly bodies around it and all
motion as ‘uniform,’ that is, unchanging.

But observers realized that the heavenly bodies did not move as
Aristotle postulated. The earth was not the true center of the orbits
and the motion was not uniform. The most obvious problem was that the
outer planets seemed to stop, move backwards in
‘retrograde’ motion for a while, and then continue
forwards. By the second century, when Ptolemy compiled his
Almagest (this common name of Ptolemy's Syntaxis was
derived from its Arabic title), astronomers had developed the concept
that the orbit moves in ‘epicycles’ around a
‘deferrent,’ that is, they move like a flat heliacal coil
around a circle around the earth. The earth was also off-center, on an
‘eccentric,’ as the heavenly bodies moved around a central
point. Ptolemy added a point on a straight line opposite the
eccentric, which is called the ‘equalizing point’ or the
‘equant,’ and around this point the heavenly bodies moved
uniformly. Moreover, unlike the Aristotelian model, Ptolemy's
Almagest did not describe a unified universe. The ancient
astronomers who followed Ptolemy, however, were not concerned if his
system did not describe the ‘true’ motions of the heavenly
bodies; their concern was to ‘save the phenomena,’ that
is, give a close approximation of where the heavenly bodies would be
at a given point in time. And in an age without professional
astronomers, let alone the telescope, Ptolemy did a good job plotting
the courses of the heavenly bodies.

Not all Greek astronomical ideas followed this geocentric
system. Pythagoreans suggested that the earth moved around a central
fire (not the sun). Archimedes wrote that Aristarchus of Samos
actually proposed that the earth rotated daily and revolved around the
sun.[3]

During the European Middle Ages, the Islamic world was the center of
astronomical thought and activity. During the ninth century several
aspects of Ptolemy's solar theory were recalculated. Ibn al-Haytham in
the tenth-eleventh century wrote a scathing critique of Ptolemy's
work: “Ptolemy assumed an arrangement that cannot exist, and the
fact that this arrangement produces in his imagination the motions
that belong to the planets does not free him from the error he
committed in his assumed arrangement, for the existing motions of the
planets cannot be the result of an arrangement that is impossible to
exist” (quoted in Rosen 1984, 174). Swerdlow and Neugebauer
(46–48) stressed that the thirteenth-century Maragha school was also
important in finding errors and correcting Ptolemy: “The method
of the Maragha planetary models was to break up the equant motion in
Ptolemy's models into two or more components of uniform circular
motion, physically the uniform rotation of spheres, that together
control the direction and distance of the center of the epicycle, so
that it comes to lie in nearly the same position it would have in
Ptolemy's model, and always moves uniformly with respect to the
equant.” They found that Copernicus used devices that had been
developed by the Maragha astronomers Nasir al-Din Tusi (1201-1274),
Muayyad al-Din al-Urdi (d. 1266), Qutb al-Din al-Shirazi (1236-1311),
and Ibn al-Shatir
(1304–1375).[4]
In addition, Ragep, 2005, has shown that a theory for the inner
planets presented by Regiomontanus that enabled Copernicus to convert
the planets to eccentric models had been developed by the
fifteenth-century, Samarqand-trained astronomer Ali Qushji
(1403–1474). The problem is, as Goddu (476–86) has pointed out, we
have no proof of their transmission from east to west. Nevertheless,
it is highly unlikely that so many similar techniques were invented
independently in the west.

Renaissance humanism did not necessarily promote natural
philosophy, but its emphasis on mastery of classical languages and
texts had the side effect of promoting the sciences. Georg Peurbach
(1423–1461) and (Johannes Müller) Regiomontanus (1436–1476)
studied Greek for the purpose of producing an outline of Ptolemaic
astronomy. By the time Regiomontanus finished the work in 1463, it was
an important commentary on the Almagest as well, pointing
out, for example, that Ptolemy's lunar theory did not accord with
observations. He noted that Ptolemy showed the moon to be at various
times twice as far from the earth as at other times, which should make
the moon appear twice as big. At the time, moreover, there was active
debate over Ptolemy's deviations from Aristotle's requirement of
uniform circular motion.

It is impossible to date when Copernicus first began to espouse
the heliocentric theory. Had he done so during his lecture in Rome,
such a radical theory would have occasioned comment, but there was
none, so it is likely that he adopted this theory after 1500. Further,
Corvinus, who helped him print his Latin translation in 1508–09,
expressed admiration for his knowledge of astronomy, so that
Copernicus's concept may have still been traditional at this point. His
first heliocentric writing was his Commentariolus. It was a
small manuscript that was circulated but never printed. We do not know
when he wrote this, but a professor in Cracow cataloged his books in
1514 and made reference to a “manuscript of six leaves
expounding the theory of an author who asserts that the earth moves
while the sun stands still” (Rosen, 1971, 343; MW
75). Thus, Copernicus probably adopted the heliocentric theory
sometime between 1508 and 1514. Rosen (1971, 345) suggested that
Copernicus's “interest in determining planetary positions in
1512–1514 may reasonably be linked with his decisions to leave his
uncle's episcopal palace in 1510 and to build his own outdoor
observatory in 1513.” In other words, it was the result of a
period of intense concentration on cosmology that was facilitated by
his leaving his uncle and the attendant focus on church politics and
medicine.

It is impossible to know exactly why Copernicus began to espouse
the heliocentric cosmology. Despite his importance in the history of
philosophy, there is a paucity of primary sources on Copernicus. His
only astronomical writings were the Commentariolus, the
Letter against Werner, and On the Revolutions; he
published his translation of Theophylactus's letters and wrote the
various versions of his treatise on coinage; other writings relate to
diocesan business, as do most of the few letters that survive. Sadly,
the biography by Rheticus, which should have provided scholars with an
enormous amount of information, has been lost. Therefore, many of the
answers to the most interesting questions about Copernicus's ideas and
works have been the result of conjecture and inference, and we can
only guess why Copernicus adopted the heliocentric system.

Most scholars believe that the reason Copernicus rejected
Ptolemaic cosmology was because of Ptolemy's
equant.[5]
They assume this because of what Copernicus wrote in the
Commentariolus:

Yet the widespread [planetary
theories], advanced by Ptolemy and most other [astronomers], although
consistent with the numerical [data], seemed likewise to present no
small difficulty. For these theories were not adequate unless they
also conceived certain equalizing circles, which made the planet
appear to move at all times with uniform velocity neither on its
deferent sphere nor about its own [epicycle's]
center…Therefore, having become aware of these [defects], I
often considered whether there could perhaps be found a more
reasonable arrangement of circles, from which every apparent
irregularity would be derived while everything in itself would move
uniformly, as is required by the rule of perfect motion.
(MW 81).

Goddu (381–84) has plausibly maintained that while the initial
motivation for Copernicus was dissatisfaction with the equant, that
dissatisfaction may have impelled him to observe other violations of
uniform circular motion, and those observations, not the rejection of
the equant by itself, led to the heliocentric theory. Blumenberg (254)
has pointed out that the mobility of the earth may have been
reinforced by the similarity of its spherical shape to those of the
heavenly bodies.

As the rejection of the equant suggests a return to
the Aristotelian demand for true uniform circular motion of the
heavenly bodies, it is unlikely that Copernicus adopted the
heliocentric model because philosophies popular among Renaissance
humanists like Neoplatonism and Hermetism compelled him in that
direction.[6]
Nor should we attribute Copernicus's desire for uniform circular
motions to an aesthetic need, for this idea was philosophical not
aesthetic, and Copernicus's replacing the equant with epicyclets made
his system more complex than Ptolemy's. Most importantly, we should
bear in mind what Swerdlow and Neugebauer (59) asserted:

Copernicus arrived at the heliocentric theory by a careful analysis of
planetary models — and as far as is known, he was the only
person of his age to do so — and if he chose to adopt it, he did
so on the basis of an equally careful analysis.

In the Commentariolus Copernicus listed assumptions that
he believed solved the problems of ancient astronomy. He stated that
the earth is only the center of gravity and center of the moon's
orbit; that all the spheres encircle the sun, which is close to the
center of the universe; that the universe is much larger than
previously assumed, and the earth's distance to the sun is a small
fraction of the size of the universe; that the apparent motion of the
heavens and the sun is created by the motion of the earth; and that
the apparent retrograde motion of the planets is created by the
earth's motion. Although the Copernican model maintained epicycles
moving along the deferrent, which explained retrograde motion in the
Ptolemaic model, Copernicus correctly explained that the retrograde
motion of the planets was only apparent not real, and its appearance
was due to the fact that the observers were not at rest in the
center. The work dealt very briefly with the order of the planets
(Mercury, Venus, earth, Mars, Jupiter, and Saturn, the only planets
that could be observed with the naked eye), the triple motion of the
earth (the daily rotation, the annual revolution of its center, and
the annual revolution of its inclination) that causes the sun to seem
to be in motion, the motions of the equinoxes, the revolution of the
moon around the earth, and the revolution of the five planets around
the sun.

The Commentariolus was only intended as an
introduction to Copernicus's ideas, and he wrote “the
mathematical demonstrations intended for my larger work should be
omitted for brevity's sake…” (MW 82). In a sense
it was an announcement of the greater work that Copernicus had
begun. The Commentariolus was never published during
Copernicus's lifetime, but he sent manuscript copies to various
astronomers and philosophers. He received some discouragement because
the heliocentric system seemed to disagree with the Bible, but mostly
he was encouraged. Although Copernicus's involvement with official
attempts to reform the calendar was limited to a no longer extant
letter, that endeavor made a new, serious astronomical theory
welcome. Fear of the reaction of ecclesiastical authorities was
probably the least of the reasons why he delayed publishing his
book.[7]
The most important reasons for the delay was that the larger work
required both astronomical observations and intricate mathematical
proofs. His administrative duties certainly interfered with both the
research and the writing. He was unable to make the regular
observations that he needed and Frombork, which was often fogged in,
was not a good place for those observations. Moreover, as Gingerich
(1993, 37) pointed out,

[Copernicus] was far from the major international centers of printing
that could profitably handle a book as large and technical as De
revolutionibus. On the other [hand], his manuscript was still
full of numerical inconsistencies, and he knew very well that he had
not taken complete advantage of the opportunities that the
heliocentric viewpoint offered…Furthermore, Copernicus was far
from academic centers, thereby lacking the stimulation of technically
trained colleagues with whom he could discuss his work.

The manuscript of On the Revolutions was basically
complete when Rheticus came to visit him in 1539. The work comprised
six books. The first book, the best known, discussed what came to be
known as the Copernican theory and what is Copernicus's most important
contribution to astronomy, the heliocentric universe (although in
Copernicus's model, the sun is not truly in the center). Book 1 set
out the order of the heavenly bodies about the sun: “[The sphere
of the fixed stars] is followed by the first of the planets, Saturn,
which completes its circuit in 30 years. After Saturn, Jupiter
accomplishes its revolution in 12 years. The Mars revolves in 2
years. The annual revolution takes the series' fourth place, which
contains the earth…together with the lunar sphere as an
epicycle. In the fifth place Venus returns in 9 months. Lastly, the
sixth place is held by Mercury, which revolves in a period of 80
days” (Revolutions, 21–22). This established a
relationship between the order of the planets and their periods, and
it made a unified system. This may be the most important argument in
favor of the heliocentric model as Copernicus described
it.[8]
It was far superior to Ptolemy's model, which had the planets
revolving around the earth so that the sun, Mercury, and Venus all had
the same annual revolution. In book 1 Copernicus also insisted that
the movements of all bodies must be circular and uniform, and noted
that the reason they may appear nonuniform to us is “either that
their circles have poles different [from the earth's] or that the
earth is not at the center of the circles on which they revolve”
(Revolutions, 11). Particularly notable for Copernicus was
that in Ptolemy's model the sun, the moon, and the five planets seemed
ironically to have different motions from the other heavenly bodies
and it made more sense for the small earth to move than the immense
heavens. But the fact that Copernicus turned the earth into a planet
did not cause him to reject Aristotelian physics, for he maintained
that “land and water together press upon a single center of
gravity; that the earth has no other center of magnitude; that, since
earth is heavier, its gaps are filled with water…”
(Revolutions, 10). As Aristotle had asserted, the earth was
the center toward which the physical elements gravitate. This was a
problem for Copernicus's model, because if the earth was no longer the
center, why should elements gravitate toward it?

The second book of On the Revolutions elaborated the
concepts in the first book; book 3 dealt with the precession of the
equinoxes and solar theory; book 4 dealt with the moon's motions; book
5 dealt with the planetary longitude and book 6 with
latitude.[9]
Copernicus depended very much on Ptolemy's observations, and there
was little new in his mathematics. He was most successful in his work
on planetary longitude, which, as Swerdlow and Neugebauer (77)
commented, was “Copernicus's most admirable, and most demanding,
accomplishment…It was above all the decision to derive new
elements for the planets that delayed for nearly half a lifetime
Copernicus's continuation of his work — nearly twenty years
devoted to observation and then several more to the most tedious kind
of computation — and the result was recognized by his
contemporaries as the equal of Ptolemy's accomplishment, which was
surely the highest praise for an astronomer.” Surprisingly,
given that the elimination of the equant was so important in the
Commentariolus, Copernicus did not mention it in book 1, but
he sought to replace it with an epicyclet throughout On the
Revolutions. Nevertheless, he did write in book 5 when
describing the motion of Mercury:

…the ancients allowed the epicycle to move uniformly only
around the equant's center. This procedure was in gross conflict with
the true center [of the epicycle's motion], its relative [distances],
and the prior centers of both [other circles]…However, in order
that this last planet too may be rescued from the affronts and
pretenses of its detractors, and that its uniform motion, no less than
that of the other aforementioned planets, may be revealed in relation
to the earth's motion, I shall attribute to it too, [as the circle
mounted] on its eccentric, an eccentric instead of the epicycle
accepted in antiquity (Revolutions, 278–79).

Although Copernicus received encouragement to publish his book from
his close friend, the bishop of Chelmo Tiedemann Giese (1480–1550),
and from the cardinal of Capua Nicholas Schönberg (1472–1537), it
was the arrival of Georg Joachim Rheticus in Frombork that solved his
needs for a supportive and stimulating colleague in mathematics and
astronomy and for access to an appropriate printer. Rheticus was a
professor of mathematics at the University of Wittenberg, a major
center for the student of mathematics as well as for Lutheran
theology. In 1538 Rheticus took a leave of absence to visit several
famous scholars in the fields of astronomy and mathematics. It is not
known how Rheticus learned about Copernicus's theory; he may have been
convinced to visit Copernicus by one of the earlier scholars he had
visited, Johann Schöner, though, as Swerdlow and Neugebauer (16)
noted, by “the early 1530's knowledge of Copernicus's new theory
was circulating in Europe, even reaching the high and learned circles
of the Vatican.” Rheticus brought with him some mathematical and
astronomical volumes, which both provided Copernicus with some
important material and showed him the quality of the mathematical
printing available in the German centers of
publishing.[10]
Rheticus's present of the 1533 edition of Regiomontanus's On all
Kinds of Triangles (De triangulis omnimodis), for
example, convinced Copernicus to revise his section on
trigonometry. But Rheticus was particularly interested in showing
Copernicus the work of the Nuremberg publisher Johann Petreius as a
possible publisher of Copernicus's volume. Swerdlow and Neugebauer
(25) plausibly suggested that “Petreius was offering to publish
Copernicus's work, if not advertising by this notice that he was
already committed to do so.” Rheticus wrote the Narratio
prima in 1540, an introduction to the theories of Copernicus,
which was published and circulated. This further encouraged
Copernicus to publish his Revolutions, which he had been
working on since he published the
Commentariolus.

The Narratio prima was written in 1539 and took the form
of a letter to Johann Schöner announcing Copernicus's findings
and describing the contents of the Revolutions. He dealt with
such topics as the motions of the fixed stars, the tropical year, the
obliquity of the ecliptic, the problems resulting from the motion of
the sun, the motions of the earth and the other planets, librations,
longitude in the other five planets, and the apparent deviation of the
planets from the ecliptic. He asserted that the heliocentric universe
should have been adopted because it better accounted for such
phenomena as the precession of the equinoxes and the change in the
obliquity of the ecliptic; it resulted in a diminution of the
eccentricity of the sun; the sun was the center of the deferents of
the planets; it allowed the circles in the universe to revolve
uniformly and regularly; it satisfied appearances more readily with
fewer explanations necessary; it united all the spheres into one
system. Rheticus added astrological predictions and number mysticism,
which were absent from Copernicus's work.

The Narratio prima was printed in 1540 in Gdansk (then
Danzig); thus, it was the first printed description of the Copernican
thesis. Rheticus sent a copy to Achilles Pirmin Gasser of Feldkirch,
his hometown in modern-day Austria, and Gasser wrote a foreword that
was published with a second edition that was produced in 1541 in
Basel. It was published again in 1596 as an appendix to the first
edition of Johannes Kepler's Mysterium cosmographicum (Secret
of the Universe), the first completely Copernican work by an
adherent since the publications by Copernicus and Rheticus.

The publication of Rheticus's Narratio prima did not
create a big stir against the heliocentric thesis, and so Copernicus
decided to publish On the Revolutions. He added a dedication
to Pope Paul III (r. 1534–1549), probably for political reasons, in
which he expressed his hesitancy about publishing the work and the
reasons he finally decided to publish it. He gave credit to
Schönberg and Giese for encouraging him to publish and omitted
mention of Rheticus, but it would have been insulting to the pope
during the tense period of the Reformation to give credit to a
Protestant
minister.[11]
He dismissed critics who might have claimed that it was against the
Bible by giving the example of the fourth-century Christian apologist
Lactantius, who had rejected the spherical shape of the earth, and by
asserting, “Astronomy is written for astronomers”
(Revolutions, 5). In other words, theologians should not
meddle with it. He pointed to the difficulty of calendar reform
because the motions of the heavenly bodies were inadequately
known. And he called attention to the fact that “if the motions
of the other planets are correlated with the orbiting of the earth,
and are computed for the revolution of each planet, not only do their
phenomena follow therefrom but also the order and size of all the
planets and spheres, and heaven itself is so linked together that in
no portion of it can anything be shifted without disrupting the
remaining parts and the universe as a whole”
(Revolutions, 5).

Rheticus returned to Wittenberg in 1541 and the following year
received another leave of absence, at which time he took the
manuscript of the Revolutions to Petreius for publishing in
Nuremberg. Rheticus oversaw the printing of most of the text.
However, Rheticus was forced to leave Nuremberg later that year
because he was appointed professor of mathematics at the University of
Leipzig. He left the rest of the management of printing the
Revolutions to Andrew Osiander (1498–1552), a Lutheran
minister who was also interested in mathematics and astronomy. Though
he saw the project through, Osiander appended an anonymous preface to
the work. In it he claimed that Copernicus was offering a hypothesis,
not a true account of the working of the heavens: “Since he [the
astronomer] cannot in any way attain to the true causes, he will adopt
whatever suppositions enable the motions to be computed correctly from
the principles of geometry for the future as well as for the past
…these hypotheses need not be true nor even probable”
(Revolutions, xvi). This clearly contradicted the body of the
work. Both Rheticus and Giese protested, and Rheticus crossed it out
in his copy.

Copernicus's fame and book made its way across Europe over the
next fifty years, and a second edition was brought out in
1566.[12]
As Gingerich's census of the extant copies showed, the book was read
and commented on by astronomers. Gingerich (2004, 55) noted
“the majority of sixteenth-century astronomers thought
eliminating the equant was Copernicus' big achievement.”

While Martin Luther may have made negative comments about
Copernicus because the idea of the heliocentric universe seemed to
contradict the
Bible,[13]
Philip Melanchthon (1497–1560), who presided over the curriculum at
the University of Wittenberg, eventually accepted the importance of
teaching Copernicus's ideas, perhaps because Osiander's preface made
the work more palatable. His son-in-law Caspar Peucer (1525-1602)
taught astronomy there and began teaching Copernicus's work. As a
result, the University of Wittenberg became a center where
Copernicus's work was studied. But Rheticus was the only Wittenberg
scholar who accepted the heliocentric idea. Robert Westman (1975a,
166–67) suggested that there was a ‘Wittenberg
Interpretation’: astronomers appreciated and adopted some of
Copernicus's mathematical models but rejected his cosmology, and some
were pleased with his replacement of the equant by epicyclets. One of
these was Erasmus Reinhold (1511–1553), a leading astronomer at
Wittenberg who became dean and rector. He produced a new set of
planetary tables from Copernicus's work, the Prutenic
Tables. Although, as Gingerich (1993, 232) pointed out, “there
was relatively little to distinguish between the accuracy of the
Alfonsine Tables and the Prutenic Tables,” the
latter were more widely adopted; Gingerich plausibly suggested that
the fact that the Prutenic Tables more accurately predicted a
conjunction between Jupiter and Saturn in 1563 made the
difference. Reinhold did not accept the heliocentric theory, but he
admired the elimination of the equant. The Prutenic Tables excited
interest in Copernicus's work.

Tycho Brahe (1546–1601) was the greatest astronomical observer
before the invention of the telescope. He called Copernicus a
‘second Ptolemy’ (quoted in Westman 1975, 307) and
appreciated both the elimination of the equant and the creation of a
planetary system. But Tycho could not adopt the Copernican system,
partly for the religious reason that it went against what the Bible
seemed to preach. He, therefore, adopted a compromise, the
‘geoheliostatic’ system in which the two inner planets
revolved around the sun and that system along with the rest of the
planets revolved around the earth.

Among Catholics, Christoph Clavius (1537–1612) was the leading
astronomer in the sixteenth century. A Jesuit himself, he incorporated
astronomy into the Jesuit curriculum and was the principal scholar
behind the creation of the Gregorian calendar. Like the Wittenberg
astronomers, Clavius adopted Copernican mathematical models when he
felt them superior, but he believed that Ptolemy's cosmology —
both his ordering of the planets and his use of the equant — was
correct.

Pope Clement VII (r. 1523–1534) had reacted favorably to a talk
about Copernicus's theories, rewarding the speaker with a rare
manuscript. There is no indication of how Pope Paul III, to whom
On the Revolutions was dedicated reacted; however, a trusted
advisor, Bartolomeo Spina of Pisa (1474–1546) intended to
condemn it but fell ill and died before his plan was carried out (see
Rosen, 1975). Thus, in 1600 there was no official Catholic position on
the Copernican system, and it was certainly not a heresy. When
Giordano Bruno (1548–1600) was burned at the stake as a heretic,
it had nothing to do with his writings in support of Copernican
cosmology, and this is clearly shown in Finocchiaro's reconstruction
of the accusations against Bruno (see also Blumenberg's part 3,
chapter 5, titled “Not a Martyr for Copernicanism: Giordano
Bruno”).

Michael Maestlin (1550–1631) of the University of Tübingen
was the earliest astronomer after Rheticus to adopt Copernicus's
heliocentricism. Although he wrote a popular textbook that was
geocentric, he taught his students that the heliocentric system was
superior. He also rejected Osiander's preface. Maestlin's pupil
Johannes Kepler wrote the first book since the publication of On
the Revolutions that was openly heliocentric in its orientation,
the Mysterium cosmographicum (Secret of the Universe). And,
of course, Kepler eventually built on Copernicus's work to create a
much more accurate description of the solar system.

A. Complete Works of Copernicus

In 1972 the Polish Academy of Sciences under the direction of
J. Dobrzycki published critical editions of the Complete
Works of Copernicus in six languages: Latin, English, French,
German, Polish, and Russian. The first volume was a facsimile edition.
The annotations in the English translations are more
comprehensive than the others. The English edition was reissued as
follows:

B. Other Translations of Copernicus's Works

On the Revolutions of the Heavenly Spheres, 1955,
trans. C.G. Wallis, vol. 16 of Great Books of the Western
World, Chicago: Encyclopedia Britannica; 1995, reprint, Amherst:
Prometheus Books.

On the Revolutions of the Heavenly Spheres, 1976,
trans. and ed. A.M. Duncan, Newton Abbot: David & Charles.

“The Derivation and First Draft of Copernicus's Planetary
Theory: A Translation of the Commentariolus with Commentary,”
1973, trans. N.M. Swerdlow, Proceedings of the American
Philosophical Society, 117: 423–512.